All about Internet Relay Chat

IRC servers with code based on old Ratbox 2.0 code are vulnerable to a bug in the code that handles user authentication. It was found and published at 7 pm GMT by IRC member Fudge when he messed around with the protocol TS6. Charybdis developer nenolod was informed about the issue in the development channel #charybdis. Shortly after that him and other members agreed on that the bug was “pretty serious”.

A working example of how an IRC server could be brought down via this bug was published in the channel. Some person, or a group people, began to misuse the information they presumably got from the channel in order to bring down Efnet. At 10:45 pm GMT, many servers have been patched and restarted, but there are still ten servers, including services.int [Update: services.int is down due to unrelated maintenance according to EFnet], missing, according to the automatically updated network map on http://map.efnet.net/. To bring a server down, the attacker does not need any special privileges. All they would need to do is to send one line consisting of less than 15 characters.

A new version of Charybdis was released around 22.00 pm later this same evening. Patch files for both Ratbox and Charybdis have been sent to many IRC administrators, so that they can secure their servers against this exploit as soon as possible.

Some of the affected channels include #irchelp, a channel that now has a new date of creation:-!- Channel #irchelp created Mon Dec 31 22:32:01 2012

It is likely that the operators of #chanfix will get a dramatically increased work load during the next couple of hours. They have prepared well by setting the topic of the channel:Yes we know EFnet just took a mickey. Plz state the channel with the problem and wait…

There are rumours around claiming Hybrid is also affected, but they have not been confirmed [Update 2: According to the IRCd-Hybrid team, it is not affected by the vulnerability]. As the number of IRC servers forked from Ratbox, with exploitable code, is relatively high it is highly likely that servers on many networks will go up and down for the next few days.

Freenode was one of the first networks to patch themselves, occuring only minutes after the seriousness of the issue had been established. Thanks to staff member tomaw all relevant servers could be secured before any harm was done.

IRC servers which have been confirmed by their developers as patched against this vulnerability are: